Modern industrial, commercial aerospace and military systems depend critically on reliable pumps for fluid handling. Both gas and liquid fluids take advantage of smaller, more distributed and more portable systems for increasing uses in instrumentation and control.
Although important advances in pump technology have been made in the past few decades, progress has been slowed down considerably in the ability to reduce pump size, weight, power consumption and cost. There remains a large gap between the technology for conventional pumps, including micropumps, and more advanced pumps based on microelectronics technology.
The pumping range of micropumps is from about one to tens of microliters per minute. Thus they are useful for applications such as implantable systems for drug delivery or micro dosage for chemical analysis systems. However, pump speeds are still too slow for use in sampling applications. Pressure sensing can at times require rapid reports of any change in pressure, particularly to anticipate a major change in pressure before it fully takes place.
It has been proposed to use mesoscopic pumps with no rotating or sliding parts, with high electrical-to-pneumatic conversion efficiencies. These meso pumps have significantly increased the capabilities of military systems that detect chemical biological, explosive or other  agents. Some of these pumps are disclosed in U.S. Pat. No. 5,836,750, in which a plurality of chambers, such as, for example, three or four chambers, each of which having a single diaphragm. The devices are admirably suited for the intended purpose, but have some limitations in other aspects. Of prime concern is the presence of lateral channels, which result in dead space.
To overcome this situation, an improved electrostatic pump has been developed, as described in U.S. Pat. No. 6,179,586. In this patent, the pump consists of a single molded plastic chamber with two thin diaphragms staked directly on top of each other. The diaphragms are actuated, depending on design, with electrostatic, electromagnetic or piezoelectric methods. This patent describes the use of a single chamber for pumping.
While this prior patent also is a major improvement in the art, it does have some limitation. For example, the prior patent requires metalization and dielectric patterning of the molded plastic parts. The method of sensing does not permit the use of the same device to sense positive pressure and negative pressure without modifying the device. The prior art patent causes both diaphragms to move together as part of the pumping action. It does not disclose any other use of the structure.
It would be of great advantage if a pressure sensor could be developed that would utilize conventional mesopump construction and would have other uses. 
Another advantage would be if mesopump technology could be modified to provide accurate pressure sensing devices for both liquid and gas, and for positive and negative pressures.
Other advantages and features will appear hereinafter. 